JP2007195848A - Induction heating cooker and method of manufacturing induction heating cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an induction heating cooker with little possibility of separation of a coating film caused by the rise of the internal pressure of the coating film applied to the inner surface of the cooker, even if a heat insulating layer is formed on the outer surface of a cooking container with a carbon set body as a heating element. <P>SOLUTION: The induction heating cooker has the cooking container to be induction-heated by a heating coil. The cooking container is made of the carbon set body 1 as the heating element, and is characterized by the coating film on the outer surface of the carbon set body 1. The coating film includes continuous pores C which communicate with the carbon set body 1 and which are opened on the outer surface of the carbon set body 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a cooking container of an induction heating type cooking device that performs cooking by electromagnetic induction heating. More specifically, the present invention is provided with a coating film having pores on an outer surface which is a non-cooking surface and is provided with heat insulation. It relates to cooking containers.

  In a conventional electromagnetic induction heating cooker cooking container, a clad plate in which a ferritic stainless steel plate or the like, which is a magnetic metal, is combined with the outer side of a nonmagnetic metal aluminum material or the like as a base material is pressed, for example, a pan After being molded into a shape, an inner surface used for cooking is coated with a fluororesin having excellent non-sticking properties.

  In an induction heating type cooker, a clad pan using a clad material made of a material capable of induction heating is inserted into a container cover, a heating coil is provided in close contact with the outside of the container cover, and high-frequency current is supplied to the heating coil. The clad pan is induction-heated.

  The clad material used in induction heating cookers has a low thermal conductivity, such as a ferritic stainless steel plate, which is a magnetic metal, and is only about 1 mm thick. The temperature change and heating unevenness that occur without being able to quickly reflect the amount of heat generated by the change in amount occur.

  Therefore, in the cooking container of the induction heating type cooker, a high heat conductive material mainly composed of nonmagnetic metal aluminum is used together with the clad material so that the heat generated at the bottom can be transmitted to the entire container and uniformly heated. Therefore, after finishing heating and stopping the high-frequency current, there is a problem that the cooking container in a high temperature state is easily cooled.

Induction with a simple structure to form a heat insulation layer consisting of multiple minute closed spaces on the outside of the container in order to enhance the heat insulation performance of the outer surface of the container, cook with less uneven heating, and keep warm with high heat insulation performance. A heating cooker has been proposed (see, for example, Patent Document 1).
JP-A-10-211091

  It is suitable for cooking that it is easy to generate far infrared rays by suppressing temperature unevenness and slowing temperature change with a cooking container using carbon condensate with high heat conductivity and capable of electromagnetic induction heating. Has been.

  In order to obtain a cooking container with high heat insulation performance, when a heat insulating layer consisting of a fine closed space is formed outside the cooking container using carbon aggregate as a raw material, the carbon aggregate adheres to and penetrates the cooking utensils of the cooking container. The internal pressure of the coating is reduced by the heating and heating of the air in the pores of the carbon condensate and the water that has entered from the outside. There exists a subject of producing the situation which raises and tends to cause peeling of a coating film.

  The present invention has been made to solve the above-described problems. Even if a heat insulating layer is formed on the outer surface of the cooking vessel using the carbon aggregate as a heating element, the inner pressure of the coating film applied to the inner surface of the cooking vessel. It is an object of the present invention to provide an induction heating cooker and a method of manufacturing an induction heating cooker that are less likely to cause peeling of a coating film.

  The induction heating cooker according to the present invention is an induction heating cooker having a cooking container that is induction-heated by a heating coil. The cooking container is composed of a carbon aggregate that serves as a heating element, and is formed on the outer surface of the carbon aggregate. A coating film containing continuous pores that open to the outer surface and communicate with the carbon aggregates is formed.

  The induction heating cooker according to the present invention has the above-described configuration to provide heat retention to the outer surface, which is a heat radiating portion of the cooking container, and to continuously contain the gas in the voids included in the carbon aggregate in the coating film. It is possible to obtain a cooking container that is discharged by the pores and suppresses an increase in the internal pressure of the coating film, and the coating film is hardly peeled off.

Embodiment 1 FIG.
FIG. 1 to FIG. 6 are diagrams showing Embodiment 1, FIG. 1 is a manufacturing process diagram of a pot-shaped workpiece, FIG. 2 is an outer surface coating process diagram of the pot-shaped workpiece, and FIG. 3 is a conceptual diagram of a silicone resin impregnation state. ((A) is a conceptual diagram of a silicone resin impregnated state in the vicinity of a painted surface, (b) is a conceptual diagram of a reinforcing state between particles), FIG. 4 is an inner surface painting process diagram of a pot-shaped workpiece, and FIG. FIG. 6 is a conceptual diagram of pores formed by shrinking a dispersed polypropylene foam, and FIG. 6 shows an inner pot (this embodiment; (A)) in which a paint mixed with hollow particles is coated on the outer surface, and no hollow particles are filled. It is the figure which compared the heat retention performance of the inner pot (Comparative example; (B)) which coated the silicone resin on the outer surface.

  Using a carbon condensate that generates heat by receiving induction current due to the magnetic field generated by the current flowing in the heating coil of the induction heating cooker, and achieves uniform heating based on excellent thermal conductivity to improve rice cooking performance The manufacturing method of the inner pot (an example of a cooking container) of a rice cooker (an example of an induction heating type cooking device) will be described in detail below.

First, the manufacturing process of a carbon aggregate is demonstrated with reference to FIG. A raw material mainly composed of coke powder is heated to 300 ° C., added with a petroleum tar pitch in a molten state, kneaded, and then pressed to form a block to form a precursor (S10). The precursor is sintered in an oxygen-free state at 1000 ° C. (S20), and further heat-treated in an oxygen-free state at 3000 ° C. (S30), so that the carbon has a purity of 99.9% or more and a density of about 1.7 g. A carbon aggregate of / cm ³ is obtained. The carbon aggregate is cut using a lathe and processed into a hook shape with a thickness of 5 mm, thereby completing a hook-like workpiece (S40). At this time, it is important to remove the cutting waste by sucking it at the time of cutting so that the cutting waste does not remain in the pores and impede impregnation with the liquid resin described later.

  Next, the process of coating the outer surface of the hook-shaped workpiece will be described with reference to FIG. This embodiment is characterized by the outer surface coating of this pot-shaped workpiece. The paint used is a polypropylene having a diameter of 0.02 to 0.1 mm and a foaming ratio of 20 to 30 times in a silicone resin (an example of a resin having heat resistance equal to or higher than cooking temperature) using 20% by volume thinner as a solvent. Foam fine particles (an example of thermoplastic resin foam fine particles) are contained in an amount of 50% by volume and uniformly dispersed. After coating using a roller or the like, the coating film on the outer surface is formed by curing.

  However, the pot-shaped work formed by the condensation of carbon is porous and has many voids between the particles. In other words, since there are few parts where the carbon particles are in contact with each other and the particles are missing, the lack of the particles easily occurs, so simply applying the coating surface causes the coating surface to cohesively break down from directly below the outermost surface portion of the carbon particles. Come and peel easily. Furthermore, since carbon itself is also inferior in adhesiveness with resin, there is a problem that interfacial peeling occurs when the pores on the surface of the hook-shaped workpiece are small.

  For this reason, the same composition as the above-mentioned silicone resin, diluted with a thinner so that the viscosity becomes 300 cP, is applied as a primer to the outer surface of the pot-shaped workpiece by spraying (S50). Then, in order to ensure the state which maintained uncured, drying for 10 minutes is performed at the low temperature of 150 degreeC (S60).

  Through the steps S50 and S60, as shown in FIG. 3, the carbon aggregate 1 which is the base material in the vicinity of the outer surface of the pot-shaped workpiece is impregnated with the silicone resin 2 of the paint to reinforce the bond between the carbon particles 1a. At the same time, the apparent adhesiveness can be improved by allowing the silicone resin 2 to enter the voids 1b formed by the condensed carbon particles 1a.

  Furthermore, silicone resin 2, which is a paint for coating the outer surface of the pot-shaped workpiece, contains 50% by volume of polypropylene foam fine particles having a foaming ratio of 20 to 30 times and a diameter of 0.02 to 0.1 mm, and is uniformly dispersed. The applied paint is applied using a roller or the like (S70). Since the silicone resin 2 is preliminarily applied as a primer, a coating film in which polypropylene foam fine particles larger than the diameter of the void 1b are formed on the outermost surface by impregnating only the silicone resin 2 into the void 1b of the carbon aggregate 1 It will not be in an excessively contained state. In addition, since the silicone resin 2 impregnated in the carbon aggregate 1 is in an uncured state, it is compatible with the silicone resin 2 coated on the upper layer and can exhibit a strong adhesive force.

  Next, for example, drying is performed at approximately 150 ° C. for 15 minutes (S80). The melting point of polypropylene is 165 to 176 ° C., and drying is performed at a temperature lower than this melting point. Thereafter, a coating film is formed by curing at approximately 280 ° C. for 20 minutes (S90). In the curing process of S90, the polypropylene foam filled in the coating film melts and contracts to become a non-foamed state. At this time, since the polypropylene foam has a size of 1/20 or less, voids are formed in the silicone resin coating surface of the formed outer surface coating film (details will be described later).

  In addition, when the resin liquid which only mixed the solvent into the silicone resin 2 is applied, if the coating film thickness becomes excessive, the solvent is not diffused smoothly and stays in the coating film, causing the coating film to swell. Sometimes. Therefore, the thickness of the coating film is 50 μm at the maximum.

  On the other hand, the coating film obtained by mixing the polypropylene foam fine particles and obtained by the coating process shown in FIG. 2 can be thickly coated, and the thickness can be ensured to about 300 μm.

Next, the inner surface coating of the pot-shaped workpiece will be described with reference to FIG.
First, 10 volume% of FEP (tetrafluoroethylene / hexafluoropropylene copolymer (4.6 fluoride)) fine powder is dispersed in an aqueous dispersion of PES (polyether sulfone) to reduce the pressure to 200 cP (centipoise). Using a liquid resin that is a viscosity as a primer, and using a spray to divide it into multiple times using a spray so that the inner surface corresponding to the cooking surface of the pot-like processed product is sufficiently impregnated into the pot-like processed product, It sprays until it remains thinly on the surface (S100).

  Thereafter, the liquid resin sprayed on the inner surface of the pot-shaped workpiece is secured in a dry state by heat treatment at 200 ° C. for 20 minutes (S110). A fine powder of PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) that is compatible with FEP is uniformly attached to the surface where the liquid resin is dried (S120). Then, it melt | dissolves by the heating for 30 minutes in a 370-400 degreeC furnace, and forms the inner surface coating film of the kettle-like processed material of a carbon aggregate by smooth PFA thin film (S130).

  The coating of fluororesin (FEP, PFA) formed on the inner surface of the pot-shaped workpiece by the process of FIG. 4 forms a coating film that does not contain pores such as pinholes. Even if it is used for cooking, it does not leak, and even if burnt due to excessive heating occurs, it has a feature that there is little risk of sticking, which is convenient for use as a cooking container.

  On the other hand, the pot-shaped processed product used for cooking rice with the above-mentioned coating is a vaporization of moisture entering from defective parts due to the expansion of air in the voids existing inside the carbon aggregates generated during heating or surface damage. May increase the internal pressure. If the coating on the outer surface is sealed and sealed, an outward stress is generated in the coating film on the inner and outer surfaces, so stress that causes peeling at sites that are poorly adhered to the carbon aggregate. Will occur.

  According to FIG. 5, the outer surface coating of the pot-shaped workpiece according to the present embodiment is caused by the expansion of air in the voids present inside the carbon aggregates generated during heating, the vaporization of moisture entering from defective portions due to surface damage, etc. The mechanism of formation of continuous pores that suppresses the increase in internal pressure due to is described. When the silicone resin 2 which is a thermosetting liquid resin containing a solvent is applied and dried, the polypropylene foam fine particles disappear and fine pores C are formed. A body 3 (an example of a coating film) is formed.

  In the thickness direction, the fine pores C generated by disappearance of the filled polypropylene foam particles easily undergo shrinkage deformation, and the shrinkage stress generated along with the solvent diffusion is absorbed by the pores C.

  On the other hand, since the pores C are constrained to each other in the plane direction and are difficult to shrink, the tensile stress acts and the through-hole A between the pores C where the polypropylene foam particles are in contact or excessively close to each other. Aki. Further, in the thin film portion of the silicone resin 2, fine cracks B that are generated in the thickness direction under an immature cured state communicate between the pores C. Thereby, continuous pores C communicating with the carbon aggregate and opening on the outer surface are formed in the coating film.

  Here, silicone resin is used as the paint, but it is not limited to this as long as the resin has heat resistance equal to or higher than the maximum temperature that the cooking utensil receives. For example, heat such as epoxy resin or polyester resin can be used. In addition to the curable resin, polyphenylene sulfide (PPS), polysulfone (PSU) may be used if the inner surface of the cooking vessel is not subjected to a treatment such as painting or if the temperature required for the painting is a temperature treatment such as a drying treatment with a melting point or lower. ), A thermoplastic resin having heat resistance such as polyetheretherketone (PEEK) may be used.

  In addition, the polypropylene foam fine particles used here may be replaced with other thermoplastic resins, or may be hollow fine particles instead of polypropylene foam fine particles. Furthermore, as a coating method, a method by spraying or dipping The mode may be variously modified and used.

  Next, in the inner pot of the rice cooker, in which the block of the carbon aggregate is processed into a pot-shaped molded body by cutting and the inner surface is coated with a fluororesin, the outer surface of the inner pot is coated with a coating of hollow body fine particles on the outer surface. The case of painting (this embodiment; (A)) and the case of using an inner pot coated with a silicone resin that does not fill a hollow body on the outer surface of the inner pot (comparative example; (B)) are shown below. The methods were compared for their heat retention performance.

  That is, induction heating is performed after inserting each inner pot (the inner volume is 1.4 L) of the above (A) and (B), which is adjusted to 25 ° C. by filling the rice cooker with 1.0 L (liter) of water. At this time, without giving the function of changing the input amount of the high-frequency power source suitable for rice cooking set in advance in the rice cooker, it continues to give a constant input of 600 W and cancels the input when it reaches 100 ° C I tried to do it. The heat retention performance was evaluated as (1) the temperature rising time until reaching from 25 ° C. to 100 ° C. and (2) the temperature falling time until the boiling water decreased from 100 ° C. to 40 ° C.

  The result is shown in FIG. In the case of this embodiment (A) using an inner pot coated with a silicone resin containing many pores, the heating time required for boiling of the charged water is shortened and the cooling time is extended until reaching 40 ° C. It was confirmed that it has an effect of keeping warm.

  Separately, the inner pot (the pot-like processed product coated on the inner and outer surfaces) obtained by the above manufacturing method according to the present embodiment in a vacuum is left in water, and 50 g of water is contained in the carbon aggregate. When the above-mentioned heating test was performed using the one that formed the state, the inner and outer coating films did not peel, and many water droplets adhered to the container cover inside the rice cooker. It was confirmed.

  In other words, when the inner pot made of porous carbon aggregates is heated, the internal pressure rises due to the expansion of gas such as air inside and evaporation of the invading water, etc. It has been confirmed that it has a strong bonding force with respect to the aggregate composed of carbon particles that have a function of discharging and suppressing and essentially difficult to adhere to the resin.

  In the above description, a rice cooker has been shown as an example of an induction heating type cooking device. However, in addition to this, a grill type cooking device such as a fish grilling device or a carbon material such as a toaster has excellent characteristics in generating far infrared rays. Application to various cookers that have been applied is also effective.

It is a figure which shows Embodiment 1 and is a manufacturing-process figure of a pot-shaped processed material. It is a figure which shows Embodiment 1, and is an outer surface coating process figure of a pot-shaped workpiece. FIG. 2 is a diagram showing the first embodiment, and is a conceptual diagram of a silicone resin impregnated state ((a) is a conceptual diagram of a silicone resin impregnated state in the vicinity of a painted surface, and (b) is a conceptual diagram of a reinforcing state between particles). It is a figure which shows Embodiment 1, and is an inner surface coating process figure of a pot-shaped workpiece. It is a figure which shows Embodiment 1, and is a conceptual diagram of the pore formed by shrinking the polypropylene foam disperse | distributed to the silicone resin. The figure which shows Embodiment 1 WHEREIN: The inner pot (this Embodiment; (A)) which coated the coating material which mixed the hollow particle on the outer surface, and the inner pot (silicone resin which is not filled with a hollow particle) on the outer surface (comparison) It is the figure which compared the heat retention performance of an example; (B)).

Explanation of symbols

  1 carbon aggregate, 1a carbon particles, 1b void, 2 silicone resin, 3 silicone resin porous body.

Claims (3)

In an induction heating cooker having a cooking vessel that is induction heated by a heating coil,
The cooking container is composed of a carbon aggregate serving as a heating element, and a coating film is formed on the outer surface of the carbon aggregate that includes continuous pores that communicate with the carbon aggregate and open to the outer surface. Induction heating cooker. In a method of manufacturing an induction heating cooker having a cooking vessel that is induction heated by a heating coil,
The outer surface of the cooking container having a carbon aggregate as a heating element was coated with a liquid resin diluted by dispersing a resin having heat resistance equal to or higher than the cooking temperature including foam fine particles or hollow fine particles of a thermoplastic resin in a solvent. After drying,
Furthermore, by performing a heat treatment at a temperature equal to or higher than the melting point of the thermoplastic resin constituting the foam fine particles or hollow fine particles, a coating film containing continuous pores communicating with the carbon aggregate and opening on the outer surface is formed in the cooking container. A method of manufacturing an induction heating cooker, characterized by being formed on an outer surface.   The method for producing an induction heating cooker according to claim 2, wherein the drying of the liquid resin is performed at a temperature lower than the melting point of the thermoplastic resin forming the foam fine particles or hollow fine particles.

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